col

- reverse line-feeds filter

Synopsis

col [-bfpx]

Description

The col utility reads from the standard input and writes to the
standard output. It performs the line overlays implied by reverse line-feeds, and
by forward and reverse half-line-feeds. Unless -x is used, all blank characters in
the input will be converted to tab characters wherever possible. col is
particularly useful for filtering multi-column output made with the .rt command of nroff(1)
and output resulting from use of the tbl(1) preprocessor.

The ASCII control characters SO and SI are assumed by col to
start and end text in an alternative character set. The character set to
which each input character belongs is remembered, and on output SI and
SO characters are generated as appropriate to ensure that each character is written
in the correct character set.

On input, the only control characters accepted are space, backspace, tab, carriage-return
and newline characters, SI, SO, VT, reverse line-feed, forward half-line-feed and reverse
half-line-feed. The VT character is an alternative form of full reverse line-feed,
included for compatibility with some earlier programs of this type. The only other
characters to be copied to the output are those that are printable.

The ASCII codes for the control functions and line-motion sequences mentioned above
are as given in the table below. ESC stands for the ASCII escape
character, with the octal code 033; ESC- means a sequence of two
characters, ESC followed by the character x.

reverse line-feed

ESC-7

reverse half-line-feed

ESC-8

forward half-line-feed

ESC-9

vertical-tab (VT)

013

start-of-text (SO)

016

end-of-text
(SI)

017

Options

-b

Assume that the output device in use is not capable of backspacing. In this case, if two or more characters are to appear in the same place, only the last one read will be output.

-f

Although col accepts half-line motions in its input, it normally does not emit them on output. Instead, text that would appear between lines is moved to the next lower full-line boundary. This treatment can be suppressed by the -f (fine) option; in this case, the output from col may contain forward half-line-feeds (ESC-9), but will still never contain either kind of reverse line motion.

-p

Normally, col will ignore any escape sequences unknown to it that are found in its input; the -p option may be used to cause col to output these sequences as regular characters, subject to overprinting from reverse line motions. The use of this option is highly discouraged unless the user is fully aware of the textual position of the escape sequences.

-x

Prevent col from converting blank characters to tab characters on output wherever possible. Tab stops are considered to be at each column position n such that n modulo 8 equals 1.

Environment Variables

See environ(5) for descriptions of the following environment variables that affect the execution
of col: LC_CTYPE, LC_MESSAGES, and NLSPATH.

See Also

Notes

The input format accepted by col matches the output produced by nroff
with either the -T37 or -Tlp options. Use -T37 (and the -f option
of col) if the ultimate disposition of the output of col will
be a device that can interpret half-line motions, and -Tlp otherwise.

col cannot back up more than 128 lines or handle more than
800 characters per line.

Local vertical motions that would result in backing up over the first
line of the document are ignored. As a result, the first line
must not have any superscripts.